Step 3.5 Flash (free)

Stepfun chatreasoningtool_use Long

API ID: stepfun/step-3.5-flash

Compare Calculate
Input Price
$0.10
/1M tokens
Output Price
$0.30
/1M tokens

About Step 3.5 Flash (free)

Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token. It is a reasoning model that is incredibly speed efficient even at long contexts.

💰
Price Ranking
#697 lowest price among 1240 Chat models

Model Specifications

Context Length
262k
Max Output
66k
Release Date
2026-01-29
Capabilities
chat reasoning tool_use
Input Modalities
text
Output Modalities
text

Best For

  • Complex reasoning, math problems, multi-step logic
  • Conversations, content writing, general assistance

Consider Alternatives For

  • Image understanding (needs vision capability)
  • Simple Q&A (cheaper models available)

💰 Real-World Cost Examples

Estimated monthly costs for common use cases

Personal AI Assistant
$0.14
/month
50 conversations/day, ~500 tokens each
Customer Service Bot
$4.20
/month
1000 tickets/day, ~800 tokens each
Data Analysis Pipeline
$5.85
/month
500 analyses/day, ~2k tokens each
Calculate Your Custom Usage

Stepfun Model Lineup

Compare all models from Stepfun to find the best fit

Model Input Output Context Capabilities
Step 3.5 Flash (free) Current $0.10 $0.30 262k chat reasoning tool_use
Step 3.7 Flash $0.20 $1.15 262k chat reasoning tool_use
View All Stepfun Models →

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🚀 Quick Start

Get started with Step 3.5 Flash (free) API

OpenAI-compatible SDK 
from openai import OpenAI

client = OpenAI(
    base_url="https://api.provider.com/v1",
    api_key="YOUR_API_KEY"
)

response = client.chat.completions.create(
    model="stepfun/step-3.5-flash",
    messages=[
        {"role": "user", "content": "Hello!"}
    ]
)
print(response.choices[0].message.content)

Resources

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